Usually, sheets such as copying paper sheets are formed with punched holes for filing by means of a manual or motordriven punch by setting one sheet or a plurality of stacked sheets at a predetermined position. The setting of a sheet or sheets at the predetermined position is made using a positioning guide provided on the punch or with a center mark as a guide. The positioning guide is adjusted to meet the sheet size or distance of the sheet edge from the punched holes.
Meanwhile, with recent widespread use and increase in efficiency of business machines such as plane paper copiers (PPC) or automatic paper feeders (APF) for processing sheets, there is a demand for quickly and efficiently performing the punching to form filing holes after a copying process. Japanese Patent Disclosure No. 63-121862 discloses a punch which is intended to meet the demand noted above. This punch is provided on the paper discharge side of the copier, and its punching member is operated against each of the copying sheets, which are discharged one by one by a discharging roller after a copying process, in a timed relation to the discharging of paper by a cam associated with the discharging roller, thus forming punched holes.
When punching a plurality of sheets at a time with a conventional manual or motor-driven punch, it is necessary to stack the sheets in alignment by accurately positioning them. Unless this is done, undesired departure from alignment results when the sheets are filed. In addition, if a large number of sheets are punched at a time, edge curve or burrs are formed around the punched holes. This does not present any problem when filing the punched sheets. However, when these sheets are loaded in a copier with an automatic paper feeder (APF) for copying again on these sheets, the curved edge or burrs noted above have adverse effects on smooth feeding of the sheets.
A merit of the structure disclosed in the aforementioned Japanese Patent Disclosure No. 63-121862 is that sheets after a copying process are subjected to one-by-one punching before being discharged onto a copy tray. This precludes the cumbersomeness of handling sheets in the case of punching a plurality of sheets at a time, and thus cope with the recent business processing efficiency increase. With the disclosed structure the punching member effects punching to form punched holes in sheets which are fed continuously with its vertical movement stroke provided by a cam action in association with the operation of the discharging roller.
Therefore, if the paper feed speed is too high, it can not be followed by the punching speed of vertical movement of the punching member caused by the cam function. This means that a limitation is imposed on the copying process speed increase on the copier side. Moreover, the relation between the timing when the punching member is brought into contact with paper at the time of punching and paper feed speed is liable to cause catching of the punching member on the punched hole edge, and this is undesirable for punched hole formation quality improvement.
As a measure to solve the above problem in the above prior art punch utilizing the cam action that it is difficult to form neat punched holes, the invention contemplates stopping sheets being fed temporarily at a punching position and cause punching operation of the punching member while the sheets are stationary. To have sheets stopped temporarily, positioning means to this end is necessary. The invention utilizes such positioning means of sheet feed position determination structures which are used in conventional time recorders, copiers and other business machines for dealing with sheets such as cards and printing or copying sheets.
As a sheet feed position determination structure in the other business machines noted above, there is a well-known structure, in which a sheet is pinched between a drive roller and a pinch roller to be fed and held stationary for a while by starting and stopping the drive roller with a stepping motor, a servo motor or a DC motor.
FIG. 16 shows a structure which uses a stepping motor. In this structure, a sheet-like member (a) such as a printing or copying sheet is pinched between a drive roller (c), which is driven by a stepping motor (b) as a drive motor, and a pinch roller (d) opposing the drive roller, and can be fed along a guide member (e) in the direction of arrow A in the Figure. A sensor (g) detects a reference position of the sheet-like member (a), for instance the leading end (f) thereof, and supplies a pulse corresponding to the distance from the reference position to a predetermined feed position to the stepping motor (b) through a control circuit (h). According to this pulse, the stepping motor (b) is driven to rotate the drive roller (c) and then stops it, thus stopping the sheet-like member (a) at the feed position noted above to effect feed positioning of the sheet-like member (a).
The pinch roller (d) is rotatably supported by a free end of an arm member (i) pivoted at the other end, and a spring member (j) biases the arm member (i) to urge the fed member (a) against the drive roller (c).
Designated at (k) in the Figure is a belt for transmitting the rotation of the stepping motor (b) to the drive roller (c).
FIG. 17 shows a structure using a servo motor. In the Figure, parts like those in FIG. 16 are designated by like reference symbols. In this structure, in addition to the sensor (g) an encoder (m) is provided to detect the amount of rotation of a servo motor (l) as a drive motor for detecting the feed position of the sheet-like member (a). The output of detection is fed back through the control circuit (n) to the servo motor (l) to control the servo motor (l) for determining the feed position of the sheet-like member (a).
In a structure using a DC motor, a sensor is provided at the stop position of the sheet-like member, and according to the detection of the sheet-like member by the sensor the DC motor is stopped to determine the feed position of the sheet-like member.
In the above prior art positioners for positioning sheet-like members such as cards and printing or copying sheets, however, the stepping motor or servo motor employed is expensive. Moreover, where the stepping motor is used, such complicated control as commonly termed trapezoidal control is necessary for causing gradual start and stop of the motor in order to prevent overshoot or the like. Also, where the servo motor is used, an encoder, a feedback circuit, etc. are necessary, leading to a complicated structure and circuit.
The structure using the DC motor is not so expensive. However, in order to stop the motor quickly at the time of position detection by the sensor, it is necessary to slow down the motor right before the stop position and also cause generation of a sudden electric braking force in the motor at the stop position. Therefore, the control circuit is again complicated, leading to high cost.
In either case, complicated motor control is necessary in order to prevent inertial rotation of the motor when stopping the motor to stop the sheet-like member pinched between the drive roller and pinch roller at a predetermined position.
As discussed above, the stepping motor, servo motor and DC motor can of course be used as a drive source for feeding the sheet-like member, and a structure of a mechanism for determining a punching position or like predetermined position with these motors or with a combination of these motors and a simple sensor can be sufficiently adopted. However, as seen in the other business machines noted before, a system using such motors for stopping a sheet-like member or the like in a predetermined position is complicated in its mechanical structure and control circuit structure as described. Therefore, a new mechanism for determining a feeding position is expected having a simpler structure and more reliable stop control.